A method of adding a string is known. An extra hole is here drilled into the head, after which the tuning machine is fixed in this hole. One side of the added string is here tensioned substantially parallel to an existing string, wherein the added string is tuned such that the sound is precisely an octave higher than the existing string. The other side of the added string is secured with an added string pin, for which purpose an extra hole must likewise be drilled. A surprisingly warm sound can in this way be obtained, for instance when playing a chord. The drawback of the known method is that the stringed instrument is irreversibly modified, whereby it loses value.